Conventionally, targets to be subjected to an inspection for delamination in a laminated body are mostly pipes, containers, and the like. When the inspection is performed, usually, a person enters a pipe, a container, or the like, and performs a visual inspection, a hammering test, a pinhole inspection, etc. from the inside. Therefore, operations have to be suspended during the inspection, and the inspection takes a lot of time.
Meanwhile, as an example of the aforementioned inspection method, Patent Document 1 has proposed a method of inspecting peeling of a lining without suspending the operation. The method disclosed in Patent Document 1 includes: causing an ultrasonic wave pulse to enter a pipe or a container from the outside; obtaining a region in which a variation range for each number of reflections of multiple reflection in a sound part does not overlap a variation range for each number of reflections of multiple reflection in an artificial delamination part; obtaining the number of reflections of a reflected wave, which is greater than the smallest number of reflections in the obtained region and at which the height of the region is equal to or greater than a predetermined value; receiving a multiple-reflected wave in an inspection portion of the laminated body; and comparing the received multiple-reflected wave with an echo height of a reflected wave in the sound part, obtained in advance, which is equal to or greater than a predetermined value, thereby inspecting whether or not an inter-layer delamination is present.
In the aforementioned method, however, if an obstacle such as a reinforcing plate is present on the inspection portion, a probe cannot be disposed on the surface of a test body, resulting in a region that cannot be inspected. Meanwhile, when a test region having a wide area is inspected, the entire surface of the test region needs to be scanned with a probe, resulting in an increase in the inspection time, and an increase in costs for the inspection.